I don't know of any spells, but I do know some practices which can help better establish a sleep schedule. If the issue is something like chronic insomnia, however, these things may not help very much.
First on the list is turning off electronic entertainment devices at least a half hour before bed. Screen time on your computer, phone, television, etc., is usually keeping your brain in "stay awake mode." Shutting it off and jumping into bed may be too sudden of a transition for easy sleep, and the action of getting into bed while in "stay awake" mode may be training your mind that bed time is also awake time. In stead, do something quiet like some light reading, meditating, listening to some music.
Secondly, dim the lights a bit in the evening. Our bodies are wired to respond, to some small extent, to light levels. Dimming lights, screens, etc., helps your brain think it's sunset.
Thirdly, regular bed time and wakeup time. Learn how much sleep you need to feel refreshed enough for the next day. Set an alarm in the morning, but also follow a bed time in the evening. And lead up to that bed time with preparation for bed, not just spending time on the internet or watching television.
Fourthly, stop eating at least two hours before bed. Some doctors recommend even more time. Not only can food still in your stomach lead to digestive upset, but eating is something which stimulates the brain and body. Give dinner some time to settle.
Fifthly, have a nightly ritual. It will help establish that quiet time before bed, and it will be a series of behaviors associated with going to bed and the expectation of sleep. Waiting to change into pajamas until this time is a good idea. Having a nightly shower, or at least freshening up and brushing your teeth, can be part of this. On the forum-topic-level relevance, something like a nightly prayer to your deities or a banishing ritual to be rid of metaphysical attachment from the day can be a good part of this. It's a series of things which lead to bed time, and should not be followed by more time out of bed.
Part of what this entails is removing stimulating influence, and things which may upset the body. Another part is training the brain to adjust to sleep mode when it's bed time. We humans are very prone to suggestion, and Pavlovian association is more applicable to us than many of us realize.
